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    <head>
        <meta charset="utf-8">
        <title>习题4-1</title>
        <style>
            h1{
                letter-spacing: 6px;
            }
            .b1{
                color: red;
            }
            .b2{
                color: orange;
            }
            .b3{
                color: yellow;
            }
            .b4{
                color: rgb(66, 236, 51);
            }
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    <body>
        <h1><span class="b1">五</span><span class="b2">彩</span><span class="b3">标</span><span class="b4">题</span></h1>
    </body>
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